Re: pg_upgrade and statistics

On Wed, Mar 14, 2012 at 08:26:06PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > Does anyone know how bad the queries will be with only one target?
>
> Bad. That cycle seems like largely a waste of time. About the only
> thing it would do for you is ensure that relpages/reltuples are up to
> date, which seems like something we could possibly arrange for during
> the data import.

Well, it is also getting us the most common value, which seems useful.

> > I did see if vacuumdb --analyze-only was somehow being throttled by the
> > vacuum settings, but saw the drive at 100% utilization analying a 36GB
> > table on a 24GB RAM server, so it seems I/O bound.
>
> I think it'd be good to explicitly set vacuum_cost_delay to 0 in the
> first pass, in the same way as you are forcing
> default_statistics_target, just in case somebody has a nondefault
> setting for that. The second pass could probably be allowed to use some
> higher delay setting.

OK, I have now set vacuum_cost_delay=0 for the first vacuumdb
(target=1).

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +